The present invention relates to wax formulations, in particular in the form of emulsions, methods of manufacture of such emulsions, use of the wax formulations and emulsions in the manufacture of lignocellulosic products, as well as to methods of manufacture of lignocellulosic products containing the wax formulations.
Lignocellulosic composites include a number of products made by the panel board industry, for example plywood, oriented strand board (OSB, also referred to as flake or wafer board), medium density fiber board (MDF), high density fiberboard, chipboard, laminated veneer lumber, particleboard, and the like. Such composites are formed from wood chips, wood particles and/or fibers, an adhesive binder, and optionally fillers, additives and/or processing aids. In general, the wood is mixed or treated with the binder and the other additive or filler substances, and pressed into the desired shape, i.e., boards, using a specified compacting pressure at a specified temperature range.
In both lignocellulosic composites and lumber (the wood of trees cut and prepared for use as building material) (collectively referred to herein as“lignocellulosic products”) it is desirable to control water absorption, which leads to swelling and/or shrinkage. Such dimensional instability has a detrimental affect on the utility of the product. For example, in plywood used for floor underlay, swelling causes buckling or creep in the final wood or tile overlay. Water absorption can also increase the rate of biological degradation of the product.
Waxes have been used to impart water-resistance properties to lignocellulosic products. Waxes are commonly incorporated into composites by addition to the binder, often in the form of an emulsion. Waxes can also be used to impregnate wood, again when in the form of an emulsion. Despite the existence of a number of commercially successful wax formulations, however, there remains a perceived need in the art for wax formulations with improved properties. For example, foaming may occur, or wax solids may not remain homogeneously suspended in mixtures with water-borne resins during use. Separation of the resin and wax results in non-uniformity in the water-repellency and bond quality imparted to the composite by the adhesive binder. Wax formulations usable at lower solids levels would be more economical. There is further a perceived need for improvement in the degree of water repellency imparted to the lignocellulosic product, particularly without also significantly adversely affecting the mechanical or other properties of the lignocellulosic products.
There accordingly remains a need in the art for improved wax formulations for use in lignocellulosic products, particular wax formulations that impart improved properties such as dimensional stability when the products are exposed to moisture.